WASHINGTON -- It may be hard to imagine, but I fear this election campaign is going to get worse – maybe a lot worse – before it gets better. By the time it’s done, the whole nation may feel like it needs a shower.

I base this depressing prediction on three assumptions: Polls showing the Obama coalition coming together behind Hillary Clinton are correct; Donald Trump does not want to be embarrassed as a massive loser; and the Republican Party cares more about keeping its majority in the House than about Trump’s tender feelings. Any of these premises can be wrong, but I think they’re sound.

The logical result is not pretty. Those who believed this campaign hit rock-bottom long ago should keep in mind one of Sen. John McCain’s favorite sayings: “It’s always darkest before it’s totally black.”

First the polls: Following the two conventions, Clinton has taken a clear lead over Trump. The Real Clear Politics average of recent national polls has her at 47.5 percent with Trump at 40.5 percent, by any measure a healthy advantage. Moreover, in the swing states that will decide the election, Clinton leads Trump by decisive margins in Pennsylvania, Michigan, Virginia and New Hampshire; and by a smaller but significant margin in Florida.

Ohio and North Carolina are seen as essentially tied. But a recent Atlanta Journal-Constitution poll had Clinton leading Trump by 4 points in Georgia, a red state that Democrats haven’t won since 1992. And a recent CBS/YouGov poll showed Clinton within two points of Trump in Arizona, which has voted for a Democrat only once since 1948.

In other words, if the election were held today it would be what is technically called a butt-kicking. Closer examination of the polls suggests the coalition that twice elected Barack Obama as president – led by women and minorities – is reassembling for Clinton; and that college-educated whites, who narrowly favored Mitt Romney, are moving into Clinton’s column as well.

The Trump campaign may be hoping for some sort of deus ex machina game-changer – more embarrassments from the Clinton emails, say, courtesy of Russian hackers or WikiLeaks. But that’s not a plan.

It seems to me that there are two things Trump can do. One is to raise questions in voters’ minds about Clinton. Having already called her “Crooked Hillary” and questioned her mental competence, it’s hard to imagine how the attacks could get much nastier. But I’m afraid they will.

Trump can also try to bring non-college-educated whites – his strongest demographic – out to vote in unprecedented numbers. Theoretically this might allow him to pick off a Rust Belt state or two, although it’s a long shot. “I love the poorly educated,” he said in February. He needs even more of them to love him back.

So I expect Trump to double down not just on his attacks against Clinton but on the two issues that won him his white working-class following: immigration and trade. That means more bigotry, more xenophobia and more totally unrealistic promises about the miracles that he and his team of rich-guy economic advisers will magically perform.

It doesn’t help him that the Clinton campaign has bought time during the Olympics broadcasts for an ad in which Trump acknowledges that his Trump-branded shirts are made in Bangladesh and his neckties in China. Does it even occur to Trump that anyone might ever expect him to practice what he preaches? Sorry, that was a rhetorical question.

Meanwhile, the implications of the recent polls are not lost on the GOP leadership. If Clinton defeats Trump soundly, Republicans probably will lose their majority in the Senate. But if she wins in a landslide, the party could lose control of the House as well.

“If we fail to protect our majority in Congress, we could be handing President Hillary Clinton a blank check,” House Speaker Paul Ryan wrote in an urgent fundraising appeal Thursday. Coming after a disastrous week in which Trump had attacked the Gold Star parents of a Muslim-American Army captain killed in Iraq, Ryan’s words were seen by many who follow politics as a recognition that the time may have arrived for damage control.

Some Republicans will be under increasing pressure, either from their constituents or their consciences, to distance themselves from Trump and perhaps even rescind their endorsements. How will Trump react to such betrayal? Surely by lashing out, which is how he deals with any perceived slight.

This ought to be a debate about the nation’s future. Thanks to Trump, it promises instead to be an unedifying brawl with kicking, biting and gouging allowed.

(c) 2016, Washington Post Writers Group