Getting married may affect your financial situation. After you are married, you still maintain separate credit reports and debt is most often still the responsibility of the person who incurred it. The other spouse is not automatically added to your credit card accounts. You have to actually add them to your account for them to be able to use your cards.
Even though your credit may not be affected by your spouse's bad credit, debt may greatly affect the family budget. It is important to talk about debt and finances before and after marriage. If you have not yet married (or just married), you may consider making a Prenuptial Agreement.
After marriage, it is common for spouses to take on mutual debt. Mutual debt is associated with both persons names and credit reports. From that point on, both persons are responsible for the debt, even after a divorce. Each partner is FULLY responsible for the debt, which means if one person defaults, a debt collector can collect from the other spouse or ex-spouse.