Maryland Gov. Martin O'Malley's prime-time speaking role at the Democratic National Convention on Tuesday illustrated how far he has risen in the party's ranks, but back home, the reviews of the Democrats' record are mixed.

O'Malley's coveted speaking slot, considered a springboard for rising stars, fueled speculation that O'Malley, 49, is being groomed for a 2016 presidential run. If so, he'll have to defend a record that includes unpopular tax increases, critics said.

(Read the full text of O'Malley's DNC speech)

This spring, he raised taxes for residents making more than $100,000 -- the latest in a series of tax increases since he took office in January 2007.

O'Malley has raised taxes and fees roughly 20 times since 2007, as he tries to fill chronic budget shortfalls, according to grassroots organization Change Maryland, from the income tax increase to new alcohol taxes to higher tolls on Maryland's roads and bridges. He presided over one of the largest tax increases in Maryland history in 2007, when he raised the sales tax to 6 percent from 5 percent.

"Martin O'Malley is managing the decline of Maryland," said Larry Hogan, founder and chairman of Change Maryland. The group recently released a report detailing the migration of millionaires out of Maryland after O'Malley implemented a "millionaire's tax," a temporary tax surcharge on people earning more than $1 million.

O'Malley's office disputes the accuracy of the figures and says O'Malley's tax increases were necessary to balance the budget.

"Gov. O'Malley has cut more state spending than any governor in Maryland's history -- $8 billion," O'Malley spokesman Rick Abbruzzese said in response to Change Maryland's claims. "He's protected Maryland's triple-A bond rating, which is the ultimate seal of fiscal responsibility from all three rating agencies."

O'Malley also got himself into political trouble Sunday after he answered "no" when asked on CBS' "Face the Nation" whether Americans are better off than they were four years ago.

O'Malley immediately tried to mitigate that remark, but Republicans have made it a centerpiece of their attack on Obama's stewardship over the economy.

Maryland voters also are preparing to vote in November on three controversial social issues that O'Malley has pushed: the legalization of same-sex marriage; an expansion of gambling; and the Dream Act, which would grant in-state college tuition rates to illegal immigrants.

Working with Maryland's Democratic-majority Senate and House of Delegates, he has spearheaded the state's implementation of Obamacare, and he has made record investments in education, helping Maryland's public schools win a top ranking for four straight years.