Maryland Del. Michael Hough knocks on a door while delivering campaign literature in a neighborhood on June 5 in Mount Airy, Md. (Ricky Carioti/The Washington Post)

Maryland Sen. David R. Brinkley (R-Frederick) has been wooing voters while sitting astride a horse, a gesture perhaps in keeping with his stated belief that he is riding high in his bid to win another four years in Annapolis.

But to his challenger, Del. Michael J. Hough (R-Frederick), Brinkley’s mounted sales pitch seems more elitist than effective, an apt symbol of a Republican politician who Hough says has lost touch with the average voter.

Hough, who is challenging Brinkley in the June 24 GOP primary, has been knocking on doors to defeat Brinkley, arguing that what deeply blue Maryland needs now is an arch conservative like himself.

The race between Hough and Brinkley, the Senate minority leader, is Maryland’s version of a tea-party-allied conservative trying to knock off an establishment Republican. A Hough victory in District 4 would not be as stunning as last week’s upset of House Majority Leader Eric Cantor in a Republican primary in Virginia, but it could be another sign that the tea-party-driven fight inside the GOP has plenty of life.

Hough is one of five delegates challenging a sitting senator in Maryland (a sixth delegate has dropped out but remains on the ballot). Four years ago, there were eight matchups involving senators and former or current delegates.

Maryland Sen. David Brinkley campaigns on horseback on June 16 in Hyattstown, Md. (Bonnie Jo Mount/The Washington Post)

Hough has depicted Brinkley as a traitor to conservative values, accusing him of helping Gov. Martin O’Malley (D) and the Democratic-led General Assembly push what the delegate says is an ultra-liberal agenda.

“He’s voted for 46 tax increases. I’ve voted against all tax increases,” said Hough, a resident fellow at the conservative American Legislative Exchange Council who says he is not a tea party member but welcomes the group’s support.

“Every time he reaches across the aisle, it involves the government reaching into our pockets,” Hough said of Brinkley. “To me, he’s part of the problem.”

What Hough sees as selling out, Brinkley describes as moderation. Brinkley says he has opposed O’Malley’s repeated increases in taxes and fees and accuses Hough of distorting his record. “His argument is that because I supported the budgets, I supported the tax increases, which is false. All the tax increases have separate votes, and he knows that,” Brinkley said.

Brinkley has been unapologetic about working across the aisle to get things done in a state where registered Democrats outnumber Republicans more than 2 to 1. Brinkley said he has offered alternative budgets instead of just voting nay, and he has supported some O’Malley-backed budgets because they contained important programs.

“I’ve had my say; I haven’t always had my way,” Brinkley said. “My mission has been to be effective, to be a strong conservative voice — which I am — but to also recognize realities.”

Such pragmatism, he says, has helped to secure a $750,000 bond for the Frederick County Mental Health Association, extra money for road projects and $1.8 billion for public safety, education and pensions in the county over four years. By contrast, Brinkley said, Hough has voted against measures that would benefit his constituents because he’s driven more by ideological purity than common sense.

Brinkley said he feels confident of reelection, but he acknowledged that Hough has put on an aggressive campaign.

“He’s the product of a political machine. That’s all he’s ever done is work for political operatives,” Brinkley said.

Hough, 34, lives with his wife, JoeyLynn, and their three children in Brunswick (population 6,066), about 20 miles west of Frederick on the Potomac River. An Air Force veteran, he got his start in politics working for for then-Sen. Alex X. Mooney (R-Frederick) and was elected a delegate in 2011. He recently authored a report on federalism and overreach by the U.S. government

Brinkley, 54, is divorced and lives on a small farm near Mount Airy, east of Frederick. He has two adult children. A financial consultant who specializes in estate planning, he was elected a delegate in 1995 and a senator in 2003.

Hough says that internal polls show him in the lead in the district, which includes a sliver of Carroll County and was redrawn in 2012 to pack in more Republicans and make a neighboring district safer for Democrats. He has won the backing of U.S. Rep. Andy Harris (R), former representative Roscoe Bartlett (R), Frederick County Commissioner Blaine R. Young (R) and the Red Maryland blog.

Hough had raised about $49,000 through May 20 and had nearly $110,000 in the bank. Among his contributions was a $4,000 donation from the conservative Presidential Coalition, an affiliate of Citizens United.

In the same period, Brinkley raised more than $29,000. He had more than $131,000 cash on hand, state Board of Elections records show, including a $100,000 loan from himself.

Brinkley said Hough’s campaign chest includes funds from early supporters who thought that they were backing his reelection bid for delegate, not a challenge to a sitting senator. Brinkley said he has received the backing of groups such as Maryland Right to Life, the Maryland Farm Bureau, the National Federation of Independent Business Maryland and the Maryland Fire Chiefs Association.

Campaigning recently in Mount Airy, Hough noted a Christian medallion on one resident’s vehicle. The candidate said that when he followed up with a personal message, he would remember to mention their shared faith.

“I’m going to vote for you,” said Joel Stafford, 49, an accountant whose front porch was decorated with red, white and blue bunting and who cites high taxes as his biggest concern. “I hope you win.”

Pamela Smith, 53, another voter who said she would back Hough, said she believes politicians in Annapolis have turned their backs on middle-class people such as herself.

“I don’t think they have a perspective on what our issues are,” she said.

John Wagner contributed to this report.