Washington (AFP) - Instead of an American flag, Rand Paul wears a red penny in his lapel, symbolizing the core of the politician's philosophy: no more runaway debt, and relentless submission to the US Constitution.

"We say they've taken all our money," Paul said in 2010 shortly after his stunning Senate election. "We don't have one red cent more to send them in Washington."

The 51-year-old doctor was sent to Washington by voters furious with a system that kept swelling the national debt, and anxious over what Paul sees as government zeal for war and encroachment on American civil liberties.

With political ambitions apparently extending beyond Congress, Paul might seek to test whether he can translate his appeal to the national stage.

The senator is viewed as an early standout for the 2016 Republican presidential primaries that kick off barely one year from now.

Ahead of a probable presidential campaign launch next spring, Paul announced Tuesday he will run for Senate re-election -- allowing him to crank up his campaign team for whatever lies ahead.

Five years ago barely a handful of Tea Party ultra-conservatives had heard of the ophthalmologist from Bowling Green, Kentucky who spoke truth to power and often challenged Republican Party orthodoxy.

His father Ron Paul is a firebrand former congressman from Texas, himself a three-time White House aspirant and opponent of the welfare state, and the man to whom the senator owes his political education.

"My dad has always been my dad and my political hero," Paul wrote in his 2011 book "The Tea Party Goes to Washington."

- Tea Party goes to Senate -

"I had been Tea Party before Tea Party was cool," he wrote.

When he arrived in the Senate in January 2011, the freshman took action that grabbed the attention of Washington watchers.

"President Rand Paul," the New Republic magazine proclaimed last year. Two months ago, Time magazine declared him "the most interesting man in American politics."

Story continues

His stock soared in March 2013 when he gave a 13-hour Senate speech to block confirmation of the CIA director over the Obama administration's policy on aerial drones.

Supporters quickly exhorted others to "Stand with Rand" and his opposition to abuses by the National Security Agency, a position applauded by civil liberty defenders.

The senator fancies himself a "libertarian-ish" Republican and a "constitutional conservative": he denounces federal government abuse of power and seeks to reduce its regulatory role.

In foreign policy, he deplores the 2003 invasion of Iraq and has harsh words for the war's neo-conservative architects.

He also blasts Hillary Clinton -- perhaps his most likely Democratic White House rival should he run -- as a "war hawk" for fueling calls for regime change in Syria.

Paul rejects the isolationist label, however. He has been known to cite president Ronald Reagan in insisting that dislike of war is not lack of resolve.

In an interview with AFP in 2013, he defended a realistic international approach with "a less aggressive foreign policy."

His rival Senator Marco Rubio accused Paul, without naming him, of backing the military operation against the Islamic State extremist group in large part because the American public supports it.

"Paul changes his position seemingly by the hour," sneered Michael Czin, a spokesman for the Democratic Party.

But with his reputation for fealty to the Constitution, Paul this week demanded an urgent debate and vote on a new authorization of the use of military force against IS.

He said the White House currently lacks the necessary authority to engage the jihadists without a congressional green light.

- Minorities -

Paul has gone out of his way to engage with minority groups, holding a series of listening sessions with African American community leaders.

He advocates criminal justice reform to help break the cycle of prison-unemployment-poverty that plagues many black youth, campaigns against mandatory minimum sentencing laws and seeks a restoration of voting rights for ex-convicts with non-violent offenses.

"We must realize that race still plays a role in the enforcement of the law," he said.

Democrats contest the sincerity of Paul's dedication to civil rights issues, saying he is courting votes of an overwhelmingly Democratic constituency.

The efforts allow Paul to reintroduce his party and its values, as was evident at a gathering at historically black Howard University last year.

"When the time is right, I hope that African Americans will again look to the party of emancipation, civil liberty and individual freedom," he said.