Mention the ruling parties and their candidates in the Nigerian democratic presidents

As of my last knowledge update in October 2023, here are the major ruling parties and their presidential candidates in Nigeria's democratic history since the transition to civilian rule in 1999:

1. **1999 Elections**:
- **Party**: People's Democratic Party (PDP)
- **Candidate**: Olusegun Obasanjo

2. **2003 Elections**:
- **Party**: People's Democratic Party (PDP)
- **Candidate**: Olusegun Obasanjo (re-elected)

3. **2007 Elections**:
- **Party**: People's Democratic Party (PDP)
- **Candidate**: Umaru Musa Yar'Adua

4. **2011 Elections**:
- **Party**: People's Democratic Party (PDP)
- **Candidate**: Goodluck Jonathan

5. **2015 Elections**:
- **Party**: All Progressives Congress (APC)
- **Candidate**: Muhammadu Buhari

6. **2019 Elections**:
- **Party**: All Progressives Congress (APC)
- **Candidate**: Muhammadu Buhari (re-elected)

7. **2023 Elections**:
- **Party**: All Progressives Congress (APC)
- **Candidate**: Bola Ahmed Tinubu

The above parties and candidates reflect the major political shifts in Nigeria's democracy. The PDP was the ruling party for a long time until the emergence of the APC in 2015. Following the 2023 elections, Bola Ahmed Tinubu of the APC is the current president of Nigeria.