If this is the year when 21-term Rep. Charlie Rangel finally meets defeat in a primary, his career will have come full circle.

As an ambitious state legislator in 1970, the Harlem Democrat beat longtime Rep. Adam Clayton Powell Jr. in a primary. Powell had been touched by scandal and lost the low-turnout election to Rangel by a slim margin.

More than 40 years later, Rangel, 81, is the one touched by scandal and was censured by the House for ethics violations in December 2010. Rangel’s major opponent in the June 26 primary will be state Sen. Adriano Espaillat, an ambitious legislator who represents part of the district.

But it’s not just the historical parallel that makes this election worth watching. Population shifts and redistricting means the redrawn 13th district, based in northern Manhattan and the Bronx, has a larger Hispanic population than Rangel’s current district. That could give Espaillat, a Dominican-American and former state Assemblyman, a leg up.

Forty-six percent of Rangel’s current district is Hispanic. That number jumps to more than 55 percent under the new lines in place for the 2012 elections.

The strength of Espaillat as a candidate — he has a proven base of support — means he is likely to solidify most of the anti-Rangel support.

“What Adriano represents,” explained Basil Smikle, an unaffiliated New York Democratic political consultant, “is really that one opponent that will go head-to-head with Rangel in the minds of voters. He presents that clear alternative right now.”

Smikle added, “I think it represents enough of a threat that this is a serious and interesting race.”

Espaillat, 57, announced his bid last week, saying in a statement that the people of the 13th district are “searching for leadership with bold, new ideas in Washington, D.C.”

The people who will be voting in the primary make up a much smaller universe than the district at large. And by the very nature of Rangel’s long incumbency, he remains the favorite to win two and a half months before voters go to the polls.

“It’s important to remember that the district is not that different from Rangel’s current district, where he was re-elected in the middle of his ethics issues,” one unaffiliated New York City Democratic operative said.

Rangel won his 2010 primary with 51 percent of the vote against five opponents. His closest rival pulled in only 23 percent.

“In the end, he is still an institution,” the source said. “He’s still the guy who took on Dick Cheney, and he’s still got a pretty compelling message to go give to some of these newer constituencies that are helpful to him building” a victory.

Another advantage Rangel has is the proven ability to build a broad coalition of support in the heavily minority district.

Longtime New York City Democratic consultant Bill Lynch, a Rangel adviser, articulated a view unaffiliated Democrats hold.

“A lot of people are looking at this as Latinos vs. African-Americans,” Lynch told Roll Call. “That’s not the way to look at it. He’s more than just an African-American candidate. African-Americans will support him strongly, but he’ll get a lot of Hispanic support, he’ll get a lot of labor support and he’ll get support from the white community — all people who know him and whom he has helped in his 30-plus years in the Congress.”

But those familiar with Espaillat’s campaign believe that the number of likely primary voters who haven’t made up their minds is very small and the state Senator’s narrative will appeal to those swing voters more than Rangel’s pitch. They believe general dissatisfaction with Congress, along with Rangel’s ethics issues and the changing demographics of the district, gives Espaillat a clear shot at the seat.

Rangel said in a recent statement that he is definitely running for re-election, a fact a spokesman confirmed to Roll Call last week. The filing deadline for Congress in the Empire State is April 20.

Still, the possibility remains that after more than 41 years in Congress, Rangel may decide to retire. He suffered recently from back issues that kept him hospitalized and away from the House. And as he told the New York Daily News in December 2010: “At my age, you don’t buy green bananas.”