Op-Ed: This is the last chance to get on the Trump train

The polls are making it more and more clear that election night will not be a landslide win for either Donald Trump or Hillary Clinton. For the Republicans, that means that either Trump is going to lose a close election or he will win a close election. And because the race is so tight, the GOP leaders not enthusiastically and publicly backing their nominee will be in serious trouble if they do not get on the Trump train right now.

It might already be too late for some of those Republicans, especially people like Ohio Governor John Kasich who has already said he didn't vote for Trump. But for those who haven't irreversibly denied their support, now is the time to step up. The new base of the Republican Party will not forgive any elected GOP leader who did not stand with Trump in a razor thin loss.

And the Trump team itself will most likely ignore and punish non-supportive Republicans in Washington if he wins. The polls show a strong movement of hold-out Republicans are now "coming home" to vote for Trump. Suddenly, not supporting the nominee publicly is looking like a big lose/lose for politicians who wants GOP votes.

That's a shift from the general assumption over the summer and at times this fall that Trump was likely going down in flames in a blowout loss. In that scenario, it made lots of sense for House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell, Senator Ted Cruz, and everyone with a leadership position in the Republican Congress to stay more than an arm's length from Trump at all times.

Now, the only voters Ryan, McConnell and the rest of the Republicans need to worry about are the enduring and surging Trump supporters. If Trump loses in a close election, they will almost surely punish the GOP leaders who did not show enough support for their man. Simply put: they will blame them for Trump's loss.

And if Trump wins, things could be even worse for them. A Trump administration will need allies on Capitol Hill, but a President Trump could very easily bypass Republicans who didn't back him and try to work with Democrats instead. That's especially true when it comes to Trump's policies that Republicans have opposed, like nixing the Trans-Pacific Partnership trade deal and raising the minimum wage.

It's bad enough to be a Republican Congressional leader playing second fiddle to a Republican president. But imagine how bad it will be for Ryan and McConnell if the White House chooses to ignore them altogether.

Of course, this sticky situation only applies to current elected officials. For party figureheads like the Bush family or Mitt Romney, there is no such pressure to back Trump as they are not seeking votes. Reports and rumors of the Bushes voting or at least quietly rooting for Clinton to win are significant from a philosophical and cultural point of view to be sure. But they have nothing to lose if Trumps wins or falters on November 8th.

Paul Ryan and his peers don't have that luxury. So what can they do now with just a few days left before Election Day to avoid the Trump train wrath? They can start by speaking out much more forcibly for Trump. The latest breaking news about the re-opened Clinton email probe gives them the perfect excuse to say they are now "convinced" they need to back Trump without reservation.

They may even need to do more and try to show up with Trump at a rally or two. For example, Paul Ryan should come to the next Trump event in Wisconsin or anywhere in the Midwest. Mitch McConnell is from Kentucky, but he could easily pop over to the western part of neighboring battleground state Virginia and talk up Trump there.

Cruz is already convinced, as he's at least appearing with Trump V.P. nominee Mike Pence at rallies in Michigan and Iowa Thursday. That kind of public appearance just before Election Day can sometimes stay in the voters' minds longer than they'll remember the months of sitting on the sidelines. Or they may see it as a dramatic revelation reminiscent of an Evangelical conversion.

Either way, time's running out. With the polls almost all pointing to a dead heat, the Republican leaders in Congress need to ask themselves who is more likely to reward or punish them come November 9th. Will it be the Democratic Party voters and Hillary supporters who might forgive them for not backing Trump all that much, or will it be the Republican voters and Trump supporters who might never forgive them for not backing Trump?

Commentary by Jake Novak, CNBC.com senior columnist. Follow him on Twitter @jakejakeny.

For more insight from CNBC contributors, follow @CNBCopinion on Twitter.

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