Last summer, Democrats identified six Republican-held seats on the Nov. 6 ballot as being "vulnerable" to challenges by their party’s candidates.

As of Friday, the Democrats went 0-5 in those six elections with one race – a tentative "win" – still undecided and likely headed for a recount.

As a result, incoming Senate President Bill Galvano, R-Bradenton, will lead a chamber with either a 23-17 or 24-16 GOP majority – little change from the 23-16 advantage Republicans enjoyed in 2018, but two to three votes short of the two-thirds supermajority needed to overcome a gubernatorial veto.

Unlike the Florida House, where Democrats picked up eight to 10 seats, Republicans will either gain a seat or retain the Senate advantage they’ve had since 1998.

Of the 22 races, Republicans won at least 15. The newly-seated, or re-seated, will join 18 senators – 10 Democrats, eight Republicans – whose seats are up for election in 2020.

The only one of the six races Democrats could score a win is in Tampa-area Senate District 18, where Democrat Janet Cruz, the term-limited former House Minority Leader, was leading incumbent Republican Sen. Dana Young by 355 votes in a race that is headed for a recount.

The districts where Republicans beat back Democrat challenges – mostly by convincing margins – include:

• SD 8: Republican incumbent Sen. Keith Perry defeated Democrat Kayser Enneking, a Gainesville physician, by 2,387 votes – 1.15 percent of the 202,744 ballots cast.

The race was essentially defined by the 4,277 votes – 2.11 percent – that presumedly would have gone Enneking’s way by a third-party campaign orchestrated by longtime Central Florida Democrat and former Gainesville City Commissioner Charles E. Goston.

The three SD 8 candidates combined to spend more than $3.6 million between their campaign accounts, political committees and the party support flowing in via "in-kind" contributions.

According to the state’s Division of Elections, Perry’s campaign received about $1.8 million and Enneking’s about $1.64 million to win the seat.

SD 8 includes all of Alachua and Putnam counties, and the northern half of Marion County. It is among state senate districts that became more favorable to Democrats after court-ordered redistricting before the 2016 elections.

• SD 22: Republican incumbent Sen. Kelli Stargel defeated retired circuit court judge Bob Doyel by more than 5.68 percent, tallying 105,490 votes, or 52.84 percent of the 199,658 ballots cast.

SD 22 includes northern Polk and southwestern Lake counties. Of its 348,632 registered voters, Democrats account for 126,546 for 36.3 percent of the electorate while Republicans list 117,337 voters for 33.6 percent in the district. There are 104,749 voters, or 30.1 percent, registered with no party affiliation or in third parties.

Doyel, of Winter Haven, ran unsuccessfully for a Florida House seat in eastern Polk County in 2016. He finished with 94,168 votes, or 47.16 percent of Tuesday’s ballot.

• SD 24: Republican incumbent Sen. Jeff Brandes defeated Democrat Lindsay Cross, the former executive director of the Florida Wildlife Corridor, amassing 116,370 votes for 54.28 percent of the 214,384 ballots cast.

SD 24 – which spans parts of St. Petersburg, Pinellas Park and St. Pete Beach – is among urban districts where Hillary Clinton and Barak Obama scored victories in the 2008, 2012 and 2016 elections but sent Republicans to Congress and the state legislature.

SD 16: Republican Ed Hooper defeated Democrat Amanda Murphy by 4.5 percent of the vote, garnering 111,939 votes, or 52.25 percent, to 102,312 votes, or 47.75 percent.

Hooper, a former state representative from Clearwater, will occupy the seat vacated before the 2018 legislative session by Republican incumbent Jack Latvala, who resigned amid sexual misconduct allegations, after running unopposed in 2016.

Murphy, also former state representative from New Port Richey, made the race surprisingly close in SD 16, which spans northern Pinellas and western Pasco counties.

• SD 36: Another race Democrats threatened but could not pull off as Republican State Rep. Manny Diaz defeated David Perez with 66,337 votes, or 54.09 percent, to 56,299 votes or 45.91 percent of the 122,636 ballots cast.

Diaz, who served in the Florida House from 2012 to 2018, is regarded as a rising star within the state’s GOP, so the challenge mounted by Perez, a first-time candidate and Coral Gables firefighter in the district, entirely within Miami-Dade County, served notice that GOP seats previously assumed to be "secure" may not be in coming elections.

All 22 senators elected or re-elected Tuesday to four-year terms will be in office when redistricting begins after the 2020 U.S. Census in anticipation of the 2022 mid-term elections.

Florida is among 37 states where both congressional and state legislative district lines are drawn by the state legislature.