Voters this November have the opportunity to replace or re-elect their representatives in Congress, but in most states, they'll also have the chance to make some policy themselves.

Across 39 states, there are a total of 128 initiatives and referenda on the ballot this year, according to the National Conference of State Legislatures. A referendum allows voters to approve or reject policies considered by the state legislature, while a ballot initiative lets citizens bypass state lawmakers completely to vote on an issue.

The issues on the ballot this year cover a wide range, including hot topics like marijuana legalization and raising the minimum wage. Both of those issues could help Democrats get their supporters to the polls. Ballot initiatives could play a key role in a state like Alaska, where Sen. Mark Begich, D-Alaska, is at risk of losing his seat.

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Other ballot initiatives, meanwhile, have become high-stakes battles between business interests. For instance, in California, opponents of an initiative (Proposition 46) that would raise the cap on damages in medical malpractice lawsuits have raised more than $56 million to campaign against it. Campaign spending either for or against ballot measures could surpass $1 billion this year, the Washington Post reports.

Here's a look at some of the issues voters will be considering in this year's elections:

Marijuana

Alaska's Ballot Measure 2: To regulate the production, sale and use of marijuana

Alaska is poised to follow the example set by Washington state and Colorado, which in 2012 legalized marijuana use for adults who are 21 years of age or older.

Surveys from Public Policy Polling, a Democratic firm, shows the public split. A survey taken July 31- Aug. 3 showed that 44 percent of Alaskans were in favor of the initiative, while 49 percent opposed it and 8 percent were unsure.

The Campaign to Regulate Marijuana Like Alcohol in Alaska has collected around $700,000 in contributions to promote the ballot measure, the Alaska Dispatch News reports, while the opposition group, "Big Marijuana. Big Mistake. Vote No on 2," has raised just around $40,000. However, the opposition group has the backing of groups like the Alaska Republican Party, the Alaska Chamber of Commerce and the Alaska Conference of Mayors.

Based on the outcomes of the 2012 elections in Washington and Colorado, some are predicting the marijuana measure will drive younger, more liberal voters to the polls, which should help Begich.

Oregon's Measure 91: To regulate the production, sale and use of marijuana

In 2012, Oregon voters rejected a measure to legalize marijuana by a vote of 53 percent to 46 percent. This year, they may be ready to take the leap. A poll released by Oregon Public Broadcasting in May showed that 54 percent of registered Oregon voters support legalizing marijuana for adults, while 38 percent oppose it. Another 9 percent were undecided. The poll had a 4.9 percent margin of error.

The Oregonian editorial board recently endorsed Measure 91, noting that medical marijuana has been legal in the state since 1998. "Let's be honest: Recreational marijuana is all but legal in Oregon now and has been for years," the editorial board wrote. The newspaper board also noted that Oregonians can already purchase the drug in Washington state: "A completely legal high is only a short drive away for anyone in the Portland metro area."

Meanwhile, Oregon's 36 district attorneys are all opposed to the measure, according to the Bend Bulletin.

Florida's Amendment 2: To allow the use of marijuana to treat certain medical conditions

At least 60 percent of Florida voters need to support Amendment 2 in order for it to pass, and recent polls suggest it will meet that threshold.

The nonpartisan firm Gravis Marketing found that 64 percent of registered Florida voters said they will support Amendment 2, while just 26 percent said they are opposed to it. Another 10 percent were unsure, according to the poll, which had a 4 percent margin of error. As the Orlando Sentinel notes, other polls have shown even greater support among Floridians for medical marijuana.

Democratic and Republican financiers have invested heavily in the campaigns for and against Amendment 2, which the Washington Post has characterized as a " proxy fight" for the state's competitive gubernatorial race. The Gravis poll shows a dead heat between Republican Gov. Rick Scott and his Republican-turned-Democrat challenger, former Gov. Charlie Crist.

Just three donors account for 74 percent of the money raise in support of Amendment 2, the Tampa Tribune reports, while three other donors account for nearly 99 percent of the money raised by the opposition. The biggest donor in support of Amendment 2 is John Morgan, a trial lawyer who is a Crist ally. Casino magnate Sheldon Adelson is the largest donor to the opposition campaign.

Minimum wage

Alaska's Ballot Measure 3: Increases the Alaska minimum wage to $8.75 per hour in 2015 and $9.75 per hour starting in 2016. It would thereafter be adjusted annually for inflation.

Already this year, the state minimum wage has been increased in 13 states and the District of Columbia. Democrats are now hoping to use this as a mobilizing issue in the midterms, particularly in states with key races like Alaska.

The survey released in August from Public Policy Polling showed 58 percent of Alaskans support the measure while just 33 percent oppose it.

Illinois' Minimum Wage Increase Referendum Act: Raises minimum wage for adults over the age of 18 to $10 per hour

Since this referendum is non-binding, Illinois Republicans have accused Democratic lawmakers of putting it on the ballot simply to drive Democratic turnout this November.

"Let me interpret this for you. The Dems are loading the ballot with referendums that mean nothing, just so they can get their traditional supporters out to the polls to vote for them, so they can protect their power, position, and pension," Republican state Sen. Kyle McCarter said, the Belleville News-Democrat reported earlier this year.

This week, Democratic Gov. Pat Quinn, who is up for re-election this year, began an attempt to live off of minimum wage earnings for a week and spend no more than $79.

Nebraska's Initiative 425: Raises minimum wage to $8 per hour in 2015 and to $9 per hour in 2016

The Nebraska Secretary of State's office ruled just this month that enough signatures were gathered to get Initiative 425 on the ballot.

Democrats are hopeful the initiative will help turn out more moderate and liberal voters in the solidly red state. While the governor's race and Senate race in Nebraska are expected to go to the GOP, Democrats think they have a chance at unseating Republican Rep. Lee Terry.

South Dakota's Initiated Measure 18: To raise the minimum wage for non-tipped employees from $7.25 to $8.50 per hour in 2015 and adjust annually thereafter

Even with Measure 18 on the ballot, Democrats are expected to lose a Senate seat in South Dakota. Former Republican Gov. Mike Rounds is running against Democrat Rick Weiland to replace retiring Democratic Sen. Tim Johnson. The seat is considered a " likely Republican" victory, according to the Cook Political Report.

Abortion-related measures

Colorado's Amendment 67: Defines "person" and "child" in the Colorado criminal code to include unborn human beings

Colorado voters defeated such "personhood" amendments in 2008 and 2010. This year, the amendment has become a flashpoint in the competitive race between Democratic Sen. Mark Udall and his opponent, Republican Rep. Cory Gardner.

In an ad run in April, Udall's campaign said Gardner "championed an eight-year crusade to outlaw birth control here in Colorado." Gardner supported the amendment in the past but has said he no longer supports it because it could unintentionally ban some forms of birth control.

North Dakota's Constitutional Measure 1: To "provide that the inalienable right to life of every human being at any stage of development must be recognized and protected"

In 2013, state lawmakers not only voted to put Measure 1 on the ballot, they also passed four anti-abortion rights bills that were signed into law. However, a federal judge in April overturned the Nebraska law banning abortions once a fetal heartbeat could be detected.

The anti-abortion group ND Choose Life says Measure 1 will "stop outsiders from imposing their values on us through the courts." North Dakotans Against Measure 1, meanwhile, say the measure "is poorly written and the unclear language leaves it open to interpretation - leading to more government intrusion into our personal lives."

Tennessee's Constitutional Amendment 1: To provide that nothing in Constitution of Tennessee secures or protects right to abortion or requires the funding of an abortion. It also states that the legislature retains the right to enact, amend, or repeal statutes regarding abortion, including circumstances of pregnancy resulting from rape or incest or when necessary to save the life of the mother.

Both opponents and supporters of this amendment have raised large sums for their campaigns, the Tennessean reports. As of mid-July, supporters of Amendment 1 had raised more than $518,000, while opponents had raised more than $360,000.

A Vanderbilt University poll released in May showed that 71 percent of registered Tennessee voters opposed the amendment.