Republicans have controlled the state Senate in Harrisburg for two decades.

But some Senate Democrats, buoyed by the polling lead of their candidate for governor and their own gains in the 2012 elections, contend they are on the verge of reclaiming the majority that has eluded them for a political generation.

"We're really excited,'' said Sen. Jay Costa, the Democrats' Senate leader. "We're really right on the cusp."

His opposite number, Sen. Joseph Scarnati, the Senate president pro tempore, says he's confident not just that the GOP will retain the majority, but that it has a real chance to enhance it.

"Right now, we'‍re at 27. There's an 80 percent chance we'll come back at 28; a 60 percent chance we'll come back at 29," he said last week.

Republicans held a dominant majority in the chamber going into the 2012 presidential election, with a lead of 29 to 20. But Democrats trimmed that edge to 27 to 23, picking off seats opened by GOP retirements. If they could flip just two seats in November, and if, as polls currently suggest is likely, the Democrats were also to capture the governor's mansion, they would control a tied chamber with their lieutenant governor wielding the tie-breaking gavel.

In an election in which half the seats are on the ballot, analysts see control being determined by the outcomes of the races in three open seats and a handful of GOP seats in the Philadelphia suburbs in which veteran Republican incumbents have so far prevailed against increasing Democratic strength in that corner of the state.

The retirement announcement by state Sen. Richard Kasunic, D-Fayette, earlier this year created what is probably the Republicans' best hope of picking up a currently Democratic seat. Pat Stefano, a Fayette County businessman, is the GOP candidate in the 32nd District. He faces current state Rep. Deberah Kula, D-Fayette, in the race that's a major focus for both parties. The district includes Fayette and Somerset counties and part of Westmoreland.

Republicans have designs on another southwestern seat, the 46th, which was captured by Democrat Sen. Tim Solobay of Washington County, a veteran of the House, in a heavily contested race in 2010. The GOP candidate is Camera Bartolotta, a small-business owner. Mr. Costa acknowledged that the Democrats will have to pay attention to the race, but said he is confident that Mr. Solobay will prevail once again in what is expected to be another expensive race.

The Democratic pickup opportunities are on the other side of the Susquehanna River. One of them is the newly created 40th District in the northern Lehigh Valley. A northern Allegheny County district with the same number was represented by former Sen. Jane Orie before her conviction of using public resources for campaigning; it is now in Northhampton and Monroe counties. The last round of redistricting moved the seat to accommodate the greater population growth in the eastern part of the state. The Democratic nominee there, Mark Aurand, a lawyer, won a three-way primary with 40 percent of the vote in May. He will face state Rep. Mario Scavello, who was unopposed in the GOP primary and who has been running for the seat since its creation.

Another retirement, that of state Sen. Ted Erickson, R-Delaware, created yet another open seat. Delaware County was once a GOP stronghold, but like its neighboring suburbs outside of Philadelphia, has been drifting in the Democratic direction since the 1990s. Delaware County Council President Thomas J. McGarrigle is the Republican nominee there. He faces John Kane, an official of the Plumbers Union.

The overall Democratic voting performance of the southeast has fueled Democratic hopes of picking off one or two Republican incumbents in the region, but that's a tall order, given the traditional resilience of incumbents, and the veteran status of the GOP senators in the region. Mr. Costa nonetheless expressed optimism that the region's overall voting performance in recent years will catch up with at least one of them. He cited Sens. Stewart Greenleaf, R-Montgomery, Chuck McIlhinney, R-Bucks, and Robert Tommy Tomlinson, R-Bucks, as potentially vulnerable, a characterization sharply dispute by Mr. Scarrnati.

Mr. Costa argues that the Democratic chances up and down the ballot will be enhanced by the governor's race, where polls currently show their candidate, Tom Wolf, with a significant lead over Gov. Tom Corbett. Mr. Scarnati counters that his colleagues from the Philadelphia suburbs have withstood Democratic waves in the past.

Mr. Costa said the chances for his team were bolstered by an organizational decision to unite the efforts of the Senate Democrats' campaign committee with those of the Fresh Start committee created by the Wolf campaign.

"We're being tied at the hip to the governor's race," he said.

Said Scarnati, "My good friend, Jay Costa makes that point, but many of those collar counties [Bucks, Chester, Delaware and Montgomery] voted for [former Gov.] Ed Rendell [in 2002 and 2006] but checked the Republican box for Senate."

And he predicted that perceptions of Mr. Corbett as a drag on the ticket would recede by November.

"Gov. Corbett's numbers have only one way to go -- up," he said. "And after he spends $15 million or $20 million, they will improve."

James O'Toole: jotoole@post-gazette.com

First Published: July 20, 2014, 3:08 a.m.