WASHINGTON - It was a hero's welcome Tuesday as Arizona Sen. John McCain returned to the Senate following his brain cancer diagnoses.

McCain cast the key Republican vote that starts the full Senate debate on an repeal to Obamacare -- even though nobody knows what the final bill will look like.

Arizona's senior senator then delivered a 60-minute speech letting his Senate colleagues know that was a big problem.

The Obamacare debate could eliminate health insurance coverage for more than half a million Arizonans.

"We keep trying to find a way to win without help from across the aisle," McCain said.

We verified that McCain's vote made a big difference, but the question now is, will his scalding comments affect a final vote on repealing Obamacare?

WATCH: McCain's full speech

McCain was also in Washington Tuesday in an effort to steer the annual Defense spending bill through Congress pushing for a big increase in the Pentagon budget.

McCain said he would stick around for a few days -- then return to Arizona for treatment.