MIAMI - The Mets stand alone.

After enduring the emotional swings of a season-altering homestand, after turning Citi Field into an open-air revival, after sweeping their top rivals before delirious crowds, the Mets hit the road Monday night and seized control of the National League East.

They did it emphatically, of course, as tends to be their style these days.

In a 12-1 rout of the Marlins, Yoenis Cespedes just missed hitting a pair of three-run homers, settling for the consolation prize of tying a franchise record with three doubles. It was part of a four-RBI onslaught, his first runs knocked in with the Mets.

A pair of his liners tested the structural integrity of the lime-green fences at Marlins Park, slamming the wall just a few feet from going over the fence.

Michael Conforto hit his first big-league homer, a three-run shot in the second inning that ignited the Mets, and 42-year-old Bartolo Colon allowed one run in eight innings for his first victory since June 12.

Those flourishes only added to the ultimate take-away. After entering the night in a virtual tie for first place -- just percentage points behind the Nationals -- the Mets obliterated any lingering ambiguity.

Winners of four straight, the Mets lead the NL East by themselves, the first time they have ascended to that lofty throne this late in a season since their last pennant race in 2008. The Nationals lost at home to Arizona, 6-4, to fall one game back.

The turnaround appeared unlikely when the Mets fell out of first place on June 19. At the time, their injury-ravaged lineup languished in a stretch that mushroomed into a seven-game losing streak. By July 4, they were 4 1/2 games behind the Nationals. Now, one month later, the new-look Mets have retaken the driver's seat.

The Mets spent the days leading up to last Friday's trade deadline trying to infuse life into the National League's least productive offense. They did it by trading for Kelly Johnson and Juan Uribe. They did it by promoting Conforto. They did it by beating the trade deadline to acquire a bona fide star in Cespedes.

That newfound depth shined through Monday night, and Stony Brook product Tom Koehler stood little chance. The Mets pummeled him for seven runs (six earned) in 41/3 innings and swelled his ERA against them to 14.73 in three starts this season.

By the time Koehler was chased in the fifth, he already had served up a lasting memory. It belonged to Conforto, whose first big-league homer jumped off his bat at 112 mph, according to MLB.com.

The second-inning drive disappeared on a line over the right-centerfield fence, a three-run shot that was a preview of the fireworks to come.

Colon (10-10, 4.72 ERA) gladly took the help.

The righty, 0-6 with a 6.16 ERA and a .335 opponents' batting average in seven starts since June 12, was rocked in his last outing, a season-low 2 1/3-inning beating in which the Padres pelted him for six runs and 10 hits.

But on Monday night, as Colon pitched the Mets back into first place by themselves, his problems seemed so distant. He gave up his only run in the eighth inning as he worked with a 12-run lead.