There is much ado these days about the U.S. Senate races across the country and the prospects that Republicans might recapture the Senate after eight years in the minority. Clearly, Americans are unhappy with the state of governance, and this is just the kind of disaffection that breeds significant swings in the two parties’ relative positions in the Senate (in the House, too, of course, but this year the focus is appropriately on the Senate).

The polls in various states indicate that this just might be a year of significant GOP gains, and a look at the generic realities in American politics today bolsters that perception. The University of Virginia’s Larry J. Sabato and Kyle Kondik write that a GOP Senate takeover appears to be “a probable outcome,” although they concede that the number of imponderables at this point render an outright prediction a bit premature. The New York Times suggests the Republicans have about a 61 percent chance of capturing the Senate, while political expert Charlie Cook offers a stark analytical matrix: Among Democratic-held seats, seven are in the toss-up category, two are likely GOP turnover outcomes and another is solid for a GOP pickup. Only three Republican-held seats are in toss-up territory, and none appear in clear danger of slipping to the other party.

For perspective, it might be useful to look at previous years of large partisan swings in Senate races and ponder just what kinds of political circumstances generated those developments. Let’s begin with the Great Depression, which devastated the Republican Party so thoroughly that it took decades for that party to recover.

In 1930, with the Depression raging in its early months and breeding confusion and anxiety, Republicans lost eight seats. But their position in the country had been so strong that they still held a Senate majority, with 48 seats to 47 for the Democrats. Then confusion and anxiety turned to anger, and the bottom dropped out for the party. In 1932, with Franklin Roosevelt cruising into the White House, the GOP lost another twelve seats. Two years later, they were down another eleven. In 1936, with Roosevelt capturing a second term, another eight GOP seats fell. Following the 1936 election, Republicans held only 17 seats, to 75 for the now-dominant Democrats.

This was unprecedented. Never before had a party been so devastated over so many election cycles, although the Democratic Party did lose 27 seats in the pivotal year of 1860, when the slavery issue threatened to tear the country apart.

What we see here is that the magnitude of party turnover in the Senate reflects the magnitude of national crisis. The Civil War and the Great Depression, the two greatest crises the country has ever faced, generated party turnovers that threatened the very existence of the parties adjudged to have contributed most significantly to the crises.

Smaller crises, or even perceptions of governmental dysfunction, breed smaller turnover elections. And it is interesting to track such elections with perceptions of how the country is doing—or how voters perceive the country is doing.

Take, for example, the election of 1946. Democrats had dominated the federal government—House, Senate and the White House—for fourteen years. They had brought the country through the Depression (though not speedily) and had led the nation to a World War II victory that rendered America the most powerful nation on earth. And yet the nation felt the Democrats had become stale, perhaps a bit too complacent, in their exercise of power. The result: A Democratic Senate loss of 12 seats (and 56 in the House).

But it is difficult to view this as stemming from a national consensus that the Democrats represented an underlying threat to solid government. That’s because just two years later, Democrats regained nine of the seats they had lost in 1946. They also gained 75 seats in the House, putting them ahead of where they were before the devastating 1946 results.

Indeed, the Democratic Party continued as the nation’s governing party through the ‘50s, ‘60s and ‘70s, irrespective of the party’s fluctuating prospects in presidential elections during that time. The largest turnover election was in 1958, when Democrats picked up 13 seats, marking a typical feeling of stagnation after six years of the same presidential leadership (in this instance, the Dwight Eisenhower administration).

Then came the 1980 election, with Ronald Reagan capturing the White House handily. Democrats’ standing as the nation’s unchallenged governing party came to an end. The party lost 12 seats—and control of the Senate for the first time since 1953. The Democrats retained control of the House, at least in numbers, but Reagan’s political standing in the country was such that on many major issues the Democratic leadership lost control of the floor. Thus was the GOP president able to get his budget and tax programs through Congress in the early period of his presidency.

But Reagan fell victim to the six-year syndrome that had buffeted Eisenhower thirty years earlier. The result was that in 1986 the Republicans lost eight seats and control of the Senate.

Thereafter the chamber was up for grabs depending on how voters felt about the direction of the country (and presidential leadership) at any given time. They slammed Bill Clinton in 1994, just two years into his presidency, with an eight-seat swing in Senate elections. They also generated a 52-seat swing in the House, where revelations of petty corruption riled the electorate. This sealed the Democrats’ fate as minority party in both chambers through the remainder of the decade.

No major fluctuations occurred through the first term of the George W. Bush administration. Although, the Republicans lost their razor-thin Senate majority in 2001, when the late Jim Jeffords of Vermont abandoned the GOP label and became an independent.

Then the country’s disenchantment with George W. Bush altered the balance of power significantly. In 2006, amid failed wars in Iraq and Afghanistan, voters gave the Democrats a six-seat Senate pickup. Two years later, with the country mired in its greatest economic crisis since the Great Depression, the Democrats picked up another eight seats.

By this time, the Senate vote was reflecting the electorate’s general lack of confidence in both parties, whether presidential and congressional. After giving the new Democratic president, Barack Obama, a strong majority in both the House and Senate during the later years of the Bush administration, the voters yanked on Obama’s political choke chain with a six-seat GOP Senate pickup in 2010. That’s pretty much where things stand today, after Democrats managed to regain two of those seats during Obama’s reelection year of 2012.

The prospects for a GOP takeover of the Senate reflect the country’s ongoing disaffection with government in general and Obama in particular. The president seems disengaged, disoriented as a leader and increasingly ineffective. His approval ratings in two recent polls (Gallup and Zogby) have him at around 44 percent—not as devastating as Bush’s 37 percent when his party lost 14 Senate seats in two elections, but ominous for any incumbent party.

Currently, the Democrats control 55 seats (including two independents who caucus with that party), while Republicans hold 45 seats. Hence, the GOP needs a pickup of six seats to take control.

Can the party do it? As history demonstrates, it pretty much depends on the level of national disaffection and irritation. Those sentiments seem pretty strong these days, but whether it represents a six-seat level remains a matter of speculation. But clearly the stars are aligned for a possible Senate turnover.

Robert W. Merry is political editor of The National Interest and the author of books on American history and foreign policy. His most recent book is Where They Stand: The American Presidents in the Eyes of Voters and Historians.