Part of the gathering storm for Republicans is Donald Trump's candidacy and his persistent lead in most primary polls. He is given to outlandish proposals and lacks the temperamental ballast and government experience that general election voters usually seek in a president.
As a confident (overconfident?) autodidact, he gains no benefit from the serious policy thinking of many congressional Republicans and conservative think tanks. Candidates who take such matters seriously are, for the moment anyway, overshadowed.
The Republicans' congressional party has been in disarray as well, with party rebels prompting the resignation of Speaker John Boehner. His successor, Paul Ryan, has shown a steady hand, but down the road he could face more rebellion -- along with Democrats' arguments that the squabbling makes Republicans incapable of governing responsibly.
Republicans' problems come in part because they have become over the decades a larger, more populist party. Its supporters no longer look like they belong to the same country club. Trump's support comes disproportionately from non-college-educated voters, angry at the direction of the nation and delighted with their candidate's defiance of political correctness.
Religious conservatives also make up a major Republican bloc these days; 44 percent of Mitt Romney's November 2012 voters described themselves as white evangelical Protestants. They still strongly oppose same-sex marriage, but many other Republicans, recognizing it has majority support nationally, want to drop the issue, to judge from a recent Annenberg focus group in the target state of Colorado. Holding together a large and diverse party, as Democrats have shown over the years, is a messy and sometimes off-putting business.
The gathering storm for the Democrats may be less visible to mainstream media but looms nevertheless. It was apparent in last week's House vote on pausing the entry of 10,000 Syrian refugees, when 47 Democrats joined 242 Republicans to form a veto-proof majority against the president's position.
In his press conference in Antalya, Turkey, President Barack Obama gave perfunctory assurances that the 10,000 Syrian refugees could be adequately screened, and he intimated that those who oppose his policy are un-American bigots. But after administration officials briefed House Democrats on those screening procedures, many were reportedly driven to switch and oppose the administration position.
That's evidence that the 53 percent (in a Bloomberg News poll) of voters who oppose entry for Syrian refugees have some rational basis for their views. Only 28 percent of those polled supported their entry. Democratic politicians who have to face voters likely perceive political peril in standing with the president on this issue.
There's peril as well for his party if Obama spends his last year, as he reportedly intends, advocating gun control measures -- especially after he and the Democratic presidential candidates have expressed sympathy for the demands of the Black Lives Matter group.
Homicides and violent crimes have been surging this year in many cities, quite possibly because law enforcement has cut back on active policing techniques criticized by Black Lives Matter. But gun control is not necessarily voters' preferred response. Homicides in Washington, D.C., have spiked 58 percent in 2015, and a Washington Post poll showed that concern about crime has spiked upward as well. But only half the residents of D.C., which voted 91 percent for Obama in 2012, support banning gun ownership.
The current rash of campus rebellions, with black students hurling epithets at liberal administrators, could hurt Democrats as well, making promises of "free college" look less attractive.
It's hard for a party to win a third consecutive presidential term. In the last 62 years it has happened only once, when George H. W. Bush won in 1988. Richard Nixon and Al Gore came close to doing so in 1960 and 2000.
In all three cases the incumbent president had majority job approval. In all three years America, despite facing challenges, seemed to be in a strong position in the world. Not so today. Barack Obama's job approval is currently 44 percent, and his approval rating is even lower on foreign policy.
Republicans have a chance of emerging from their gathering storm with an attractive nominee and plausible policies. Democrats seem likely to emerge from theirs with Hillary Clinton; policies dictated by an incumbent contemptuous of public opinion on major issues; and a world that seems to be spinning out of control.