Loyalty to Trump the new Republican 'litmus test': GOP representative Rep. Charlie Dent said 'litmus test' for GOP used to be conservative ideology.

 -- Republican candidates used to be measured by their conservative ideology but now are judged according to how loyal they are to President Donald Trump, GOP Rep. Charlie Dent of Pennsylvania said.

Dent, who has announced that he will not seek reelection in 2018, told ABC News' Senior Congressional Correspondent Mary Bruce in an interviewed aired on "This Week" Sunday that some Republican voters who once evaluated candidates on the purity of their conservative ideology now demand that they show complete loyalty to Trump.

"It's not about ideology anymore. It's about loyalty to the president," Dent said. "Now the litmus test has changed. The issue is loyalty to the man, to the president. And for some you know loyalty is not enough; you have to be angry and aggrieved."

The GOP representative said the president is one reason why he decided to leave Congress after this term. Dent did not endorse Trump in 2016 and also has said he didn't vote for him.

"Certainly the president has been a factor" in the decision not to seek reelection, Dent said. "You know, ... I've often said that this administration at times is taking the fun out of dysfunction. I expect a certain amount of dysfunction in government. And sometimes you can laugh at it, but it's not so funny anymore."

Dent added that he does share at least one thing in common with President Trump. He says they both are not strictly ideological but rather "pragmatic."

"I used to get lectured ... by some around here about what it means to be a good Republican ... you know, heaven forbid if you weren't completely doctrinaire on every issue," the Pennsylvania congressman said.

"I'm guilty of being pragmatic. I'm OK with that, you know, and some people aren't," Dent said. "You know, President Trump ... is very pragmatic and he likes to do deals. But at the same time you know he can't seem to get out of the way of his own Twitter feed."

The GOP representative added that he expects Republicans to lose congressional seats in 2018.

"I've told my colleagues, 'Look, we're going to be running into a headwind. You better be prepared for the worst and hope for the best. But be prepared for the worst because this could be a really tough year,” he said.