The Broad Front or Frente Amplio as it's called in Spanish has ruled Uruguay under two successive presidents since 2004. In the 2004 general election the Front secured 51.7 percent of the popular vote that put Tabare Vazquez in office as president.
In 2009 the Front retained its majority at the polls with former guerrilla fighter Jose Mujica elected as president.
Now Vazquez is back as a contender, although the 73-year-old says his candidacy still hangs on "biology" -- his own health and capacity to fulfill the five-year term. The cancer specialist is in good health but, as before and during his 2005-2010 term, not universally backed by the motley group that forms the left-wing coalition.
Most crucially, Vazquez favors closer ties with the United States, with a broader trade accord and political ties, but is opposed in that ambition by Communist and other ultra-leftist groups that want to maintain distance from Washington.
Mujica's task before handing over is to keep the Communist party on the same page as Vazquez, who is favored to win the Broad Front's nomination but only if his foes don't mount a concerted opposition. A Communist refusal to work with Vazquez will dash the Broad Front's aim to continue in power.
Communists dominate the administration of the capital Montevideo, a reward for their role in making possible the coalition's last victory in 2004 and Mujica's ascension to power.
Analysts say Mujica has more cards in his hands while dealing with the Communists than any of the old guard in the coalition. So does Senator Lucia Topolansky, Mujica's wife and like the president a former activist in the Tupamaros urban guerrilla movement.
Both received rough treatment under Uruguay's military regimes and retain misgivings about U.S. ties because the juntas fought the guerrillas with active support from the Office of Public Safety, a U.S. agency that trained and equipped police and recruited for the CIA in several Latin American countries until disbanded in the 1970s.
Still Mujica has retained a working relationship with Washington and avoided rhetoric similar to Venezuela's Bolivarian revolution.
A pragmatist with close tabs on politics of the day, Mujica has presided over Uruguay's unprecedented economic growth, fueled largely by the global commodities boom.
That growth slowed and with that downturn Mujica's popularity has slipped. Despite the reversals, however, Uruguay is rated as a well-governed state with a thriving democracy. Economic diversification is happening but progress is slow.
All that could change if the Broad Front coalition collapses because it cannot keep the Communists in its ranks or if Vazquez quits the race for reasons of health or if Vazquez faces rejection in multiparty consultations.
"It is becoming increasingly difficult for [Vazquez] to refuse such responsibility because he could then be seen as the man who precipitated the Broad Front's October 2014 defeat," Mercopress said, citing analyst and pollster Eduardo Gonzales.
Mujica has also risked public ire over initiatives to legalize marijuana, ostensibly to pull the rug under the drug warlords. Critics say the ploy will not work. Major battles are yet to be fought on abortion, with Vazquez standing on the right.
But if he's chosen as the coalition candidate the Broad Front will be confident of retaining power. With Vazquez reinstalled in the presidency, Topolansky, 68, is widely tipped to be his running mate and potential vice president, giving husband Mujica, 78, a continued say in politics from virtual retirement.
Mujica earns $12,000 a month, gives away 90 percent of his salary and shuns the official palace, living instead on a farm. The practice has won him the sobriquet of "the world's poorest president."