COLUMBUS, Ohio — Seconds into his remarks at a campaign rally last week, Republican House candidate Troy Balderson pointed out his mother in the crowd. "Mom, I'm going to protect your Social Security and Medicare. I promise. You raised me better than that," said Balderson, who aims to win Tuesday's Ohio 12th District special election on the outskirts of Columbus and surrounding areas. Protecting Social Security and Medicare are usually Democratic policy priorities. But the state senator is caught in a neck-and-neck race to win a seat his party has held for more than three decades, and he is increasingly trying to dodge criticism for saying in July that he could consider raising eligibility ages for the popular safety net programs. In an ad unveiled later in the week, Balderson sits next to his mother, who breathes with the help of an oxygen tube, and declares he would "never do anything to cut Social Security and Medicare." The Republican has shown clear concern about an energized Democratic Party's focus on health care and seniors issues as he tries to avoid losing a district that President Donald Trump won by 11 percentage points in 2016. His opponent, 31-year-old Franklin County Recorder Danny O'Connor, has tried to craft a centrist brand as he pushes to win the election and give Democrats another jolt about three months before they try to flip the House in November's midterm elections.

Democratic congressional candidate Danny O’Connor. Jacob Pramuk | CNBC

The GOP has called in the cavalry to try to avert its second special election loss in a red area this year. Not only have Trump and Vice President Mike Pence swooped into the district to campaign for Balderson, but national Republican groups have shelled out millions of dollars in an effort to paint O'Connor as a liberal pawn of House Minority Leader Nancy Pelosi. If O'Connor can prevail in the area — which is wealthier and better-educated than the median congressional seat — it would set off another blaring alarm for Republicans as they try to defend the red-leaning, suburban and rural districts they need to hold to stop Democrats from taking control of the House. "It is yet another traditionally Republican district that will suggest a blue wave if it goes Democratic or even comes close. A Democratic win here would be a big prize in moving towards a Democratic House majority, and a momentum builder," said Paul Beck, a professor emeritus of political science at Ohio State University in Columbus. Most signs point to a dead heat a day before the election in a district that encompasses suburbs, small cities and sprawling farmland mostly north and northeast of the state capital. Trump's last-minute pitch for Balderson on Saturday night followed a Monmouth University poll in which two of three voter turnout models showed only a 1 percentage-point edge for the Republican. O'Connor's campaign has outraised and outspent Balderson's. It also appeared to have a stronger canvassing and voter turnout effort based on CNBC's observations in the district last week. But Republicans have made up that gap nationally. Groups led by the House GOP-linked Congressional Leadership Fund have spent about $3.7 million opposing O'Connor and $2.4 million supporting Balderson. Only $284,000 in outside spending has gone toward backing the Democrat, and about $927,000 has been spent against the Republican.

O'Connor's pitch

O'Connor has used tactics similar to those another young Democrat, 34-year-old Rep. Conor Lamb, deployed to win a special election in a red southwestern Pennsylvania district in March. O'Connor has stressed the need to protect social programs for seniors and expand access to health care. He also swore off money from corporate donors, and promised to work with Republicans where he can. O'Connor has also tried to distance himself from Pelosi.

O'Connor could outline another potential winning blueprint for Democrats trying to prevail in red districts in November, when the party aims to flip 23 seats to take a House majority. The question is whether the Democrat can turn enough of the district blue to win — or if he will improve upon past results but fall short, as Democrats running in recent special elections in states such as Arizona, Montana and South Carolina have done. O'Connor believes grassroots energy will help to propel him to Washington, where Tuesday's winner will serve out the remainder of recently retired GOP Rep. Pat Tiberi's term. "I think the voters are ready for change. I think they're ready to have a new generation of leadership in Washington, D.C., that's focused on solving problems and not on the partisan divide," O'Connor told CNBC on Tuesday.

Balderson's balancing act

Balderson, 56, has run as a traditional Republican and backed most of Trump's priorities. He supports the GOP tax plan passed last year and efforts to repeal and replace the Affordable Care Act. Balderson wants to build the president's proposed border wall but does not support shutting down the government over funding for the barrier, as the president has threatened. Last Monday, he told reporters that he will not let loyalty to Trump stop him from looking out for the district's best interests. "I'm here to represent the 12th congressional District," he said after a rally with Pence. "That's my focus, that's my No. 1 priority. Their needs, and the values that they hold." Republicans have tried to shore up support from the GOP voters wary of Trump who could break toward O'Connor. The GOP has tried hard to emphasize turnout, and it could need every last vote from 12th District Republicans. O'Connor already has a clear advantage among independents of about 16 percentage points, according to the Monmouth survey.

The Kasich and Pelosi factors

Part of unifying the GOP hinges on highlighting an endorsement of Balderson from Ohio Gov. John Kasich, Trump's fellow Republican who embodies frustration with Trump on issues such as trade and immigration simmering within pockets of the party. In one ad sent out as part of a more than $2 million buy from the House GOP-linked Congressional Leadership Fund, Kasich says Balderson "has my vote" and "should have your vote, too." O'Connor has tried to promote his areas of agreement with Kasich, as well. He said that he is "glad that Kasich and I stand together" on certain issues. Those include supporting expansion of the federal and state Medicaid insurance program for low-income Americans and "red flag" laws that bar access to guns for people with a history of domestic violence and mental illness. On Sunday, Kasich claimed that Trump came to Ohio without an invitation from Balderson. The Republican's campaign did not immediately respond to a request to comment on whether that is true. He also contended that Trump's presence could actually hurt the Republican candidate because "the chaos that seems to surround" the president "has unnerved a lot of people." "So suburban women in particular here are the ones that are really turned off," the governor told ABC's "This Week." "And you add to that the, you know, millennials, you — you have it very close. It's really kind of shocking because this should be just a slam dunk and it's not." But national Republicans have had one notable politician on their minds more often than Kasich: Pelosi. Throughout the race, O'Connor has said he will not vote for the California Democrat for House speaker if Republicans take the House. Then, pressed repeatedly late last month during an interview with MSNBC host Chris Matthews, O'Connor said he would vote for whomever Democrats put forward for the leadership position. Republicans pounced on the comment: the National Republican Congressional Committee released a video dubbing him "Deceitful Danny." Pence called O'Connor a "Nancy Pelosi liberal" twice during his remarks last week. On Tuesday, O'Connor shrugged off the criticism as Washington intrigue and said he supports new leadership om Congress. "More Ohioans care about who our starting quarterback is going to be than inside Washington baseball," he said, while wearing a red Ohio State shirt. "And I've said from day one that I won't vote for Pelosi, I've said from day one that we need new leadership on both sides of the aisle. And insider procedural gotcha politics is never going to change that." Mark Weaver, a Republican strategist who lives in the district and supports Balderson, contended that O'Connor "had some initial success painting himself as a moderate" before he "stumbled" in the interview with Matthews. While he expects the race to tilt toward the GOP, he noted that turnout could favor O'Connor.

Red roots

The Democrat has to overcome the area's Republican roots if he wants to serve the remainder of Tiberi's term into January. O'Connor and Balderson will also face off in November to determine who will hold the seat in the next Congress. A Republican has held the seat since Kasich first won it in 1982. A handful of independent voters who spoke to CNBC in the district last week said they support O'Connor, in part because of frustration with the unified GOP government's treatment of health care. Many Republicans in the district — even some who are not the strongest Trump supporters — noted that their main goal in supporting Balderson is keeping the House in Republican hands. O'Connor, of course, is trying to prevent that. Like many Democrats trying to flip ideologically balanced or Republican-leaning districts, he has drilled into the issues of Social Security, Medicare and Medicaid frequently. Health care and those social programs typically rank among voters' top concerns across the country.

Demonstrators supporting Social Security, Medicare and Medicaid near a rally where Republican congressional candidate Troy Balderson and Vice President Mike Pence spoke. Jacob Pramuk | CNBC