Late summer surveys by CNN and other organizations show senior voters tilting decisively towards Democratic congressional candidates. That would dramatically reverse the recent pattern in midterm elections when the elderly provided a major boost to GOP candidates.

In CNN surveys conducted in early August and early September , registered voters who are 65 years of age and up preferred Democratic congressional candidates to Republicans by margins of 20 and 16 percentage points, respectively. CNN is not the only news organization to report this kind of GOP deficit among seniors. A late August Washington Post-ABC News survey found that if older voters were casting their ballots today, they would back Democratic candidates for the House of Representatives over Republican candidates by a whopping 22-point margin, 57% to 35%. Similarly, a national poll by Marist College conducted in early September found that among voters 60 years of age and up, they favored Democratic congressional candidates by a 15-point margin.

This is a potentially huge problem for Republicans: In the 2010 and 2014 midterm elections when Republicans regained control of the House and Senate, respectively, GOP candidates were solidly backed by voters 65 and up. When Democrats won control of both the House and the Senate in the 2006 midterm elections, they had a narrow advantage among senior voters.

Historically, Democrats were seen as the party of seniors. President Franklin Roosevelt made Social Security one of the landmark accomplishments of the New Deal. Decades later another Democratic president, Lyndon Johnson, would push health care coverage as an entitlement for the elderly and make Medicare one of the cornerstones of his Great Society program. In subsequent elections as social issues came to the fore, seniors have tended to split their votes more evenly or side with Republicans. But in 2010 with the rise of the Tea Party and the generational and societal change ushered in by the presidential election of Democrat Barack Obama, elderly voters turned decidedly towards the GOP. Republicans helped drive that process by asserting that president Obama's 2010 signature health care reform legislation would defund Medicare. And that would be a GOP rallying cry throughout the Obama presidency.

While exit polls showed that senior voters backed Donald Trump over Hillary Clinton for president in 2016, since he's been in office, polls suggest Trump has had difficulty maintaining elderly voters as a pillar of the Republican coalition.

Seniors are customarily more risk-averse than younger voters. Upheaval and uncertainty in government policies can make older voters apprehensive. They tend to prefer a safe and steady pair of hands to guide the ship of state. In many instances, Donald Trump has governed in an opposite manner. And his brash personal style can sometimes come across as reckless.

At the start of his term in office, CNN polling found older Americans gave president Trump fairly good job approval ratings. But that began to change with the chaotic and unsuccessful efforts by Trump and Congressional Republicans to repeal Obamacare. Elderly voters may not have been enthusiastic about the legislation to begin with, but the GOP's helter-skelter push for repeal proved equally problematic.

Trump created upheaval

Midterm elections are almost always a verdict on the incumbent president and the fortunes of Republican House and Senate candidates will ebb and flow with perceptions of Trump. By spring and early summer of this year, CNN polling found seniors fairly closely divided when asked in the so-called "generic ballot" question whether they supported the Democratic or GOP candidate in the midterm elections. At the time, Trump was not engaged in pitched battles with Congress, and he was seen to have de-escalated tensions with North Korea in the run-up and aftermath of his summit with its mercurial leader Kim Jong Un in early June.

That stasis didn't last long. When Trump took to the world stage in July, he seemed to scrap the traditional role of the U.S. president as the steady leader of the western democracies. After a contentious NATO summit in Brussels, Trump strained the "special relationship" between the U.S. and Great Britain when he undercut British Prime Minister Theresa May, telling a London newspaper that she had mishandled Brexit negotiations and speculating that her Conservative Party rival Boris Johnson might make a good prime minister. Lastly, at a summit with Russian president Vladimir Putin, Trump came across at a press conference as weak and vacillating and his performance was panned by both congressional Democrats and Republicans.

Shortly after Trump returned home, he once again adopted tough tactics for dealing with Congress, warning that he would be willing to see a government shutdown if appropriations legislation failed to include adequate funding for a border wall with Mexico and other stricter immigration measures. That is the kind of brinksmanship at which many voters, but especially seniors, can recoil. Not surprisingly, in subsequent CNN polls on the midterm elections, elderly voters abandoned Republicans and embraced Democrats.

"Older voters are much more reliable than younger ones, and if they are moving away from Trump or less likely to turn out because they don't like the way he has conducted his presidency, that is a real problem for the Republicans," observed Karlyn Bowman, a veteran public opinion analyst at the American Enterprise Institute. Trump's antagonism towards Sen. John McCain, the Arizona Republican, even after his death, may have compounded this GOP predicament. "McCain is someone seniors can relate to," said Bowman.

Older voters in key races

If older voters continue to side with Democrats, it's even more likely that they will capture enough House seats to regain the majority in that chamber. There are seniors in every House district, but some places where Republicans could be particularly vulnerable to a Democratic upset are:

Forida's 18th Congressional District (Palm Beach, Martin and St. Lucie counties), held by first-term Rep. Brian Mast

Florida's 6th Congressional District (Daytona Beach), an open seat formerly held by GOP gubernatorial nominee Ron DeSantis

Arizona's 8th Congressional District (suburban Phoenix), won by Republican Debbie Lesko in a special election in April

Michigan's 1st Congressional District (the Upper Peninsula and the northern tip of the state), represented by first-termer Jack Bergman.

All four of these seats are considered "Likely Republican" in CNN's Key Race ratings, but all four also have a senior population (65+) of more than 20%.

But it may be in the midterm Senate contests where this trend could have its most profound impact. Democrats have six potentially vulnerable Senate incumbents: Florida's Bill Nelson, Indiana's Joe Donnelly, Missouri's Claire McCaskill, Montana's Jon Tester, North Dakota's Heidi Heitkamp and West Virginia's Joe Manchin. President Trump carried those last five states by double-digit margins in the 2016 election, and he is a frequent presence in Florida, where he narrowly bested Hillary Clinton and maintains a Palm Beach retreat.

Four of those states, Florida, Montana, North Dakota and West Virginia, are among the top ten states with the highest proportion of elderly (65+) residents according to the last decennial census. (Missouri was ranked 16th and Indiana ranked 33rd.)

All of those Democratic incumbents have been elected before, and in Nelson's case, he's won three previous Senate races. They are known quantities, and if elderly voters in those states decide to look for a check on Trump, they have a familiar face to cast a ballot for.

If all of these endangered Democratic incumbents are able to win reelection and the party doesn't lose any other seat it currently holds, Democrats will only need to pick up two GOP Senate seats to claim a majority. Among the leading prospects for Democratic pick-ups are Republican seats in Arizona (ranked 18th in senior population), Nevada (44th) and Tennessee (29th). But in these contests, Democrats have a lot more than just the percentage of seniors going for them. In Arizona and Nevada, there are bulging Hispanic populations that are likely to produce droves of Democratic voters who oppose Trump's hardline immigration stance. In these two states, a good performance among elderly voters could tip the balance to the Democratic candidates.

And in Tennessee, Democrats are counting on former two-term governor Phil Bredesen to capture the seat of retiring Republican Sen. Bob Corker. Democrats hope that strong showings in urban and suburban areas in recent elections will continue for Bredesen in places like Nashville (where he was once mayor), and other major Tennessee metros. Of course, many of the new voters in those bustling areas may not have even lived in the state when Bredesen won his last election in 2006. That's why it's important for him to cut into traditional Republican bastions in rural and small town Tennessee. Those kinds of places tend to have a disproportionate share of older voters. Bredesen carried every county in the state when he was reelected governor 12 years ago, and presumably there are still rural and small town voters in Tennessee who can recall casting a ballot for him. They could be the margin that enables him to prevail.

Of course, polls can vary a lot between now and Election Day, and Democrats may not be able to sustain the hefty margins they're currently receiving from seniors in several polls. But to win back the House and the Senate, they probably don't need to. As the 2006 election showed, even a narrow margin of victory among elderly voters can help facilitate a Democratic takeover of Congress.