Republicans are heading for the exits with a Democratic wave looking more likely

Royce, who sits atop the House Foreign Relations Committee, is the 7th(!) committee chairman to announce he or she will be leaving the House in 2018. He is the 28th Republican in the House to announce he won't be running again in 2018; Democrats have just 13 open seats, by contrast.

There are, as always, mitigating circumstances. Royce, like several other committee chairmen calling it quits, is term-limited out of his chairmanship because of internal House GOP rules. Some retiring members, like Diane Black of Tennessee, are running for higher office. (Black is running for governor, a race where she is considered one of the early favorites.)

But if you take a step back from any individual retirement and look at the big picture, here's what you are left with: Veteran Republicans -- especially those in potentially competitive seats -- are opting to head for the exits rather than remain in a Congress where, if the GOP retains control this November, they would be positioned to continue to wield considerable influence.

Royce joins Rep. Ileana Ros-Lehtinen of Florida and Dave Reichert of Washington as Republican House members who represent districts Democratic presidential nominee Hillary Clinton carried in 2016 who have decided to pack it in. (Clinton won Royce's 39th District by 8 points.) There's a handful of other seats -- Charlie Dent's in Pennsylvania, Dave Trott's in Michigan, Frank LoBiondo's in New Jersey -- where Trump won but the underlying political realities of the districts suggest Democrats will make a major play to win them this fall.

In each of those cases, the retiring members are simply walking away from Congress. They aren't running for another higher office. They aren't leaving to enter the Trump administration. They don't have cushy, high-paying jobs lined up. They are just leaving.

Why? Some of it has to do with the fact that the so-called governing wing of the Republican Party -- of which most of the names above are affiliated with -- is losing steam in the nation's Capitol. Trump's takeover of the GOP during the 2016 campaign has pushed the governing end of the Grand Old Party to the fringes. Confrontation, not compromise, is now the prized goal of congressional Republicans.

Which means if that you came to Washington to get things done -- which lots of Republicans did -- you aren't having any fun at this point. And, given Trump's penchant for firing on his own troops, there's no telling if and when a Republican member of the House could be on the wrong end of a tweet from the President of the United States.

Another major factor in these retirement decisions is the increasingly dire prognosis for Republicans this November.

Trump's approval ratings have been mired in the high 30s -- at best -- for the last few months; a Gallup weekly tracking poll released Monday showed Trump's approval at 37% and his disapproval at 58%.

The average seat loss for the president's party in midterm elections since 1962 when the president's approval rating is under 50%? Try 40 seats. (Democrats need only a 24-seat gain to reclaim the majority.)

There's plenty more history here -- and none of it is good for Republicans. In the last century, the average seat loss for a president's party in his first midterm election is 23 seats. There have only been three midterm elections in the past 100 years -- 1934, 1998 and 2002 -- in which the president's party has not lost seats in a midterm.

While the history is daunting, the on-the-ground results over the past year might be even scarier for Republicans. In a series of special House elections in 2017, Democratic candidates consistently overperformed Clinton's showing in these districts. At the state legislative level, Democrats kept winning state legislative seats previously held by Republicans.

Then, in the last two months of the year, Democrats won two high-profile races: the Virginia governor's race and the special election in Alabama to replace now-Attorney General Jeff Sessions. In each of those races, Democratic base turnout soared while the Republican base was less enthused to turn out.

Combine those results, the electoral history of first term, midterm elections, Trump's dismal approval numbers and the fact that not much gets done in Washington these days, and you have a hugely toxic mix for Republicans.

Royce's retirement is an acknowledgment that his chances of winning in November were deteriorating -- and he decided he'd rather go out on his own terms. He isn't the first vulnerable Republicans to pack up his things in the face of the wave building out in the ocean right now. And he certainly won't be the last.