(CNN) Two Republican senators who have been vocal supporters of former Massachusetts Gov. Bill Weld won't say If they are open to backing his insurgent run for the Republican presidential nomination against President Donald Trump.

The silence by Republican Sens. Susan Collins of Maine and Mitt Romney of Utah is an indication of the political tight rope GOP critics of the President must walk as he runs for re-election next year. They must decide to back his campaign and satisfy Trump supporters in their states or oppose the President and potentially draw his anger and their electoral wrath.

For now, Collins and Romney are exercising a third option: Staying mum.

"I'm just not going to get into a discussion of presidential politics until 2020," said Collins, the moderate lawmaker who is facing a tough race for a fifth term in a state that tends to favor Democrats. "I just think it's premature."

Most presidents quickly win the support of lawmakers from their own parties, but Trump's demeanor in office has led some on Capitol Hill to take the extraordinary step of refusing to say if they'll back him for reelection

Read More