Circumstances have well positioned the Republicans for a chance to capture the 18th Senatorial District for the first time in a decade. Recent history suggests that opportunity does not come along often.

On Wednesday, Heather Somers made it official, announcing she was running for the seat Democratic state Sen. Andrew Maynard has held since winning it in November 2006. A who’s who of about 125 Republicans packed the meetinghouse at Olde Mistick Village for Somers’ announcement. There were Republican legislators and former legislators, mayors, first selectmen and selectmen from towns in the district, along with state party brass, notably J.R. Romano, Connecticut Republican State Party chairman. They sense victory.

Somers, 49, is a strong candidate. She has a business background. With help from a state economic development program — a point of contention in her last run for office — Somers and her partners built and eventually sold a medical device manufacturing company. As a former Groton town councilor and council-elected mayor, she has municipal experience.

Her last candidacy was for lieutenant governor as Tom Foley’s running mate. She fought her way onto the ballot, winning a 3-person primary, including capturing more than 50 percent of the vote in the 18th District she now wants to represent. The experience of running for statewide office should well prepare her for campaigning across the district consisting of Stonington, Groton, North Stonington, Griswold, Plainfield, Preston, Voluntown and Sterling.

As for losing, blame lies with Foley, who ran a lousy campaign.

The 18th is a competitive district. The interior towns lean to the right, the larger coastal towns left. In such a toss-up district, the power of incumbency means a lot. The last time the district changed hands politically there was no incumbent in the race, just like this year. In 2006, then-Sen. Cathy Cook, a Republican who had won the district in six straight elections, left the seat for an unsuccessful run at an office most voters forget even exists — comptroller.

Maynard, defeated by Cook in 2004, won in his second try, defeating veteran state Rep. Lenny Winkler, a Republican who vacated the 41st House seat she had held for two decades to run for Senate.

The reason Maynard is not running is well known and unfortunate. About four months before the 2014 election, the senator suffered a serious brain injury, falling as he tried to haul a piece of furniture up stairs outside his home at nearly 3 in the morning. Facing a weak opponent, Maynard won re-election despite being unable to campaign.

Questions about his ability to serve effectively have dogged the senator since. Concern only grew Jan. 14 when he sustained a concussion after his car struck another vehicle while traveling the wrong way on Route 32 in Waterford.

Three hours before Somers’ scheduled announcement, Maynard’s office released a statement that he would not seek re-election. That move, likely pushed by party leaders, clears a path for another Democrat, or Democrats, to enter the race. The question is who.

State Rep. Diana Urban, D-North Stonington, expressed interest, but party leaders are not thrilled at the prospect. Urban has focused on animal and child welfare issues. The key issues for most voters will be jobs and spending.

In that regard, Somers’ campaign message will be straight forward. She will run against one-party rule. For six years Democrats have controlled the state House, Senate and governor’s seat. If voters want change, goes Somers’ argument, they have to give Republicans the power to push for it.

“Our region is directly threatened by the job-crushing agenda of the Malloy administration and the chronic financial crisis that we have. That is the result of one-party rule in our legislature," Somers told supporters, who erupted with applause.

"If we don't get more Republicans elected, nothing is going to change in Hartford," she told me in an interview after the announcement.

Democrats should be worried.

Paul Choiniere is the editorial page editor.

Twitter: @Paul_Choiniere

p.choiniere@theday.com