His poll numbers in Iowa and nationally are falling among conservatives. And he clearly feels intense pressure to start acting more conservative — and quick.

One of his new, non-immigration pushes: Warning he won’t vote to fund the government unless Obamacare is thrown out. His latest speeches have made fiscal responsibility his new signature issue, including opposition to raising the debt limit unless Congress can pass a budget that balances within 10 years. And he plans to join other Republican senators in a push on abortion restrictions that will please the base, but has no chance of becoming law. …

Rubio refused to be interviewed for this column. But POLITICO’s Senate specialist, Manu Raju, cornered him in the Capitol on Wednesday to get his take.

“The Senate bill has passed the Senate,” he said. “What’s there to advocate for?” Rubio, a leader of the Gang of Eight, refused to join the rest of that gang in a meeting Tuesday with technology industry leaders to discuss putting pressure on the House. “I don’t think the best way to get a result for immigration reform in this country is to somehow try to muscle the House,” he said. The House, Rubio said, deserves “the time and space…to come up with their ideas about how to reform immigration – and I hope they will – but that’s up to them.”