Discussing the upcoming markup, Chairman Paul Ryan (R-WI) and Co Chairman Congressman Chris Van Hollen (D-MD) at the House Budget Committee on Capitol Hill Tuesday, January 24, 2012. (Melina Mara/The Washington Post)

For a full week in early October, U.S. Rep. Chris Van Hollen (D-Md.) had to stop campaigning for himself and go to work for someone else.

After President Obama’s lackluster performance in the first presidential debate, his campaign needed a strong showing by Vice President Biden in his faceoff with Rep. Paul Ryan (R-Wis.). And so Van Hollen was tapped for a key assignment: playing the Republican vice-presidential nominee to help Biden prepare.

Though they are poles apart politically, Van Hollen, the top-ranking Democrat on the House Budget Committee, knows committee chairman Ryan quite well.

“We can finish each other’s lines,” Van Hollen said, explaining that he and Ryan can read each other easily.

Van Hollen’s role as Biden’s tutor was unsurprising to allies who have known him for years. “One of our national leaders is Chris Van Hollen,” said U.S. Sen. Benjamin L. Cardin (D-Md.) at a recent business gathering in Silver Spring.

A lawyer who began his political career working for moderate Republican U.S. Sen. Charles “Mac” Mathias (Md.), Van Hollen, 53, spent 12 years in the Maryland General Assembly, first as a delegate and later as a senator. In Annapolis, he won high marks for his intellect and fiscal acumen as he played important roles in efforts to raise the state’s tax on tobacco, protect the Chesapeake Bay from pollution and require trigger locks on guns.

He is being challenged by Republican Ken Timmerman, a human rights activist and investigative reporter, in Maryland’s newly drawn 8th Congressional District.

“I got into this because this is an important election — for the country, for my children and for my grandchildren,” said Timmerman, who turns 59 on Sunday and is a neighbor of Van Hollen in Kensington.

“I realize that every child born in this country is born with $50,000 in federal debt. I think that is immoral, just immoral. We could become bankrupt like Greece,” Timmerman said.

Still, he faces an uphill battle against Van Hollen, a tenacious campaigner. In 2002, Van Hollen plotted his move to Congress carefully and knocked off Kennedy family scion Mark Shriver, a Maryland delegate, in a hard-fought Democratic primary. He then defeated moderate Republican Rep. Connie Morella in a Montgomery and Prince George’s district that had been redrawn to heavily favor Democrats.

Van Hollen’s political skills did not translate as well during his chairmanship of the Democratic Congressional Campaign Committee in 2010, when the Democrats lost the House. But he remains a member of the tight circle around House Minority Leader Nancy Pelosi (D-Calif.), is considered a key architect of the Democrats’ budget plans and keeps a high profile on international affairs.

Still, he said, he is cognizant of Tip O’Neill’s adage that “all politics is local” and is taking nothing for granted in his sixth bid for the House. This year, Van Hollen has visited the new part of the district in Frederick and Carroll counties more than 20 times, trying to woo Republican voters far from his Democratic base in Montgomery County.

“Everybody is interested in good schools for their kids, good transportation, job growth and economic development, and making sure we protect the environment in a smart way,” he said in a recent interview.

But Amy Kremer of the Tea Party Express, who had planned to campaign for Timmerman this week but was deterred by Hurricane Sandy, said the Republican’s emphasis on reducing government spending better matches voters’ views.

“People are tired of excessive spending and unsustainable debt,” she said. “We are not focused on social issues; we support fiscal responsibility, free markets and limited government.”

Timmerman criticized Van Hollen for stands such as urging the Bush administration to support a cease-fire and peacekeeping troops to end the Israel-Lebanon war in 2006. “He pretends to be a friend of Israel, and he is not,” Timmerman said.

Van Hollen, however, recently won the endorsement of Washington Jewish Week. “While we don’t necessarily agree with every policy position . . . he is a proven leader and friend, always willing to engage and perform for his district,” the newspaper said in an editorial.

The two candidates also differ on social issues that figure prominently in Maryland this fall.

Timmerman is against same-sex marriage, federal support for abortion and in-state college tuition rates for children of illegal immigrants. Van Hollen favors abortion rights. He also supports same-sex marriage and in-state tuition for illegal immigrants’ children — both issues are on the ballot in Maryland next week, as is an expansion of gambling. Van Hollen, like many prominent Democrats, has kept a low profile in the gambling debate and said he is weighing the issue; Timmerman is opposed.

Timmerman expects to raise and spend about $200,000 on the race. Van Hollen has about $2 million in his campaign treasury. While he is spending locally, he also has sent about $200,000 to help other Democrats.