Vice President Mike Pence and Republican gubernatorial candidate Ed Gillespie at a campaign rally at the Washington County Fairgrounds Saturday in Abingdon, Va. (Sara D. Davis/Getty Images)

Virginia’s gubernatorial candidates are bringing in the big guns to help them close the deal with voters. Barack Obama is coming to support Ralph Northam. Mike Pence visited on behalf of Ed Gillespie.

All this political star power is intended to get the respective bases fired up and ready to head to the polls next month.

The hard truth: They usually don’t work.

Consider a few recent examples.

  • In 2005, Republican Jerry Kilgore got a last-minute visit from then-President George W. Bush. Kilgore adviser Frank Atkinson called it  “a huge coup” to have Bush stump for Kilgore. Kilgore’s opponent, Tim Kaine, said the Bush visit would be “enormously helpful to us.” Kaine was right: He beat Kilgore 52-46 percent.
  • In 2009, President Obama campaigned for Democratic nominee Creigh Deeds. Deeds trailed Republican Robert F. McDonnell by double digits at the time of the visit, and the Obama administration had already sought to distance itself from the campaign. McDonnell defeated Deeds by more than 17 percentage points.

Or try a few older examples. The results are the same.

  • In 1977, President Carter campaigned for “old ally” Democrat Henry Howell in the 1977 race against Ted Dalton. Dalton won in a landslide.
  • In 1985, President Reagan, Vice President George H.W. Bush, former president Gerald Ford and a host of GOP luminaries made campaign appearances for Republican gubernatorial nominee Wyatt Durrette. They did nothing, and Durrette lost in a landslide to Democrat Gerald Baliles.
  • Four years later, President George H.W. Bush campaigned in the state for GOP nominee Marshall Coleman, who was running against Democratic nominee Doug Wilder. Bush painted Coleman as a valuable asset in Bush’s expanded drug war and accused Wilder of representing the “liberal creed which blames everyone except the criminal.” Wilder barely eked out a win.

Have such visits ever helped?

In 1969, President Nixon endorsed and campaigned for former staffer Linwood Holton. Thanks to deep divisions among Virginia Democrats, Holton won, becoming the first Republican to hold the state’s top job in a century.

In 2013, President Obama campaigned for eventual winner Terry McAuliffe in that year’s bruising race with Ken Cuccinelli.

By the time a current or former president arrives, the campaign narratives and issues are largely set.  It takes a special blend of circumstances, personalities and issues to make such a visit useful.

This year, we have a close contest between two nice guys. The only outside influence on the contest that matters — President Trump — has injected himself via Twitter to endorse Gillespie.

Vice President Mike Pence visited over the weekend. Pence and Gillespie are friends; Gillespie appeared with Pence during campaign swings Pence made through Virginia in 2016. On Saturday’s visit, Pence appeared in Abingdon, in the heart of Virginia’s largely rural Trump country. Even so, the event drew a crowd less than half of what was expected.

That doesn’t mean the region won’t go for Gillespie. It will. But if the Republican is intent on bringing star power to bear, he should have had Pence visit suburban and vote-rich Chesterfield County in central Virginia instead.

Chesterfield has been reliably Republican in statewide contests. It’s also something of a bellwether for how a GOP candidate will perform on election night.

The rule of thumb has been if a Republican gets 55 percent of the vote in Chesterfield, then that Republican has a very good chance to win statewide.

Republican nominees haven’t cleared that bar since the McDonnell-led ticket in  in 2009. And since 2009, Republicans are 0-7 in statewide elections.

Obama is visiting Richmond on Northam’s behalf. Northam was already going to win Richmond. But he needs the area’s African American voters, key to Democratic strength, to show up in big numbers. Obama is the one to do it — and he will be doing so in an area that, unlike Abingdon, is a statewide media hub.

Northam has played the star card more effectively, even though history says the narrative is already set, and the big names probably won’t change the race’s outcome.