The Republicans are betting big on a parlay.

In gambling, a parlay is a combination bet that only pays off when every part of the wager wins. So if I bet that the Patriots, Cowboys and Dolphins will win on Sunday, I only collect if all three win. The payoff is much greater than making three individual bets because the odds of picking three winners are worse.

Tax reform is a massive parlay.

Republicans are betting that passage of tax reform will have the desired economic effect, boosting economic growth and wages, with (politically) minimal impact on the deficit. They’re also betting that passage will dispel the widespread sense that the GOP-controlled Congress can’t get anything done. But the biggest bet is that the expected boost to the economy and the renewed sense of GOP competence will not only make this remarkably unpopular legislation popular but that a roaring economy will have a huge electoral payoff come the 2018 midterms and beyond.

Odds are good that the policy bet will pay off. If slashing business taxes, switching to a territorial tax system and giving roughly 80 percent of Americans a tax cut doesn’t stimulate economic growth, I’d be shocked. I’ll also be surprised if the deficit doesn’t go up, but the deficit hasn’t really moved many voters since Ross Perot ran for president in 1992.

The gamble that voters not already in the GOP column will suddenly see the Republicans as a competent and reliable governing party strikes me as somewhat less plausible. The last year has been more than a little chaotic. And passing tax cuts is part of Republicans’ basic job description. The fact that this is the only major legislation they could get through — in an ugly process — may not strike many persuadable voters as proof that the GOP can get other things done.

But the last bet is the real long shot. While I certainly think this legislation will become more popular — it couldn’t get less popular, given the at times absurd media coverage — it seems highly unlikely that the GOP will reverse the headwinds it’s facing in 2018.

First of all, the economy is doing quite well right now, yet President Trump’s popularity remains stuck at all-time lows for any president. A new Wall Street Journal/NBC News poll finds that Democrats have overtaken Republicans on the question of who is better at handling the economy.

Even more revealing, despite the fact that a plurality of voters (40 percent) say Trump has made the economy better, voters still don’t like him. “A president is getting credit for the economy improving and not deriving political value from it,” Republican pollster Bill McInturff told NBC. “We are watching things we have not seen before in my career.”

Trump is at 41 percent approval in the WSJ/NBC poll, which is a few ticks above the Real Clear Politics average, which has him hovering around 38 percent. But the theme is clear across polls and recent elections. The suburban, college-educated cadres that make up much of the reliable GOP base as well as the Republican-leaners who often provide the margin of victory, particularly in midterms, are simply fed up with Trump’s drama. Those voters either didn’t turn out or voted Democrat in elections in Virginia, Alabama and elsewhere, giving Democrats significant and symbolic victories.

Republicans are gambling that James Carville’s old mantra of “it’s the economy, stupid” will save them. The problem is that the economy decides the election every single time, except when it doesn’t. For instance, the polls told Mitt Romney to run against Obama on the economy. But at the end of the day, voters liked Obama more than Romney.

The irony is that Trump won in 2016 by tapping into the Nixonian insight that social issues — as defined by my old boss Ben Wattenberg in his book with Richard Scammon, The Real Majority — often decide elections. The GOP did well in the 2002 midterms by running on terrorism, not the economy.

Even the economy, like deficit, is often a stand-in for complicated attitudes about the larger direction of the country. Trump’s indictment of “the establishment” and his focus on immigration and crime were inseparable from his economic message.

The president’s party almost always suffers in midterm elections. Maybe we’ll get a roaring economy and a newfound confidence in the GOP, but, barring a war, I’ll be shocked if the GOP is not shellacked in 2018 if the most salient social issue out there remains Donald Trump.

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