Based on the search results, dark chocolate consumption does appear to have an influence on blood pressure, particularly in potentially lowering it. 

Evidence Supporting Blood Pressure Reduction

1. A Mendelian randomization study found that dark chocolate intake was significantly associated with a reduced risk of essential hypertension (EH) (OR = 0.73; 95% CI 0.60–0.88; p = 1.06 × 10−3)
   
   
2. A meta-analysis involving 31 studies showed that consuming cocoa beverages or chocolate for more than 2 weeks was associated with a reduction in systolic and diastolic blood pressure, although the effect size was small
   
   
3. A cross-sectional study involving 14,310 Jordanian adults demonstrated that dark chocolate intake has a significant beneficial effect on the blood pressure of healthy adults
   

Potential Mechanisms

1. The blood pressure-lowering effect of dark chocolate may be related to increased nitric oxide (NO) production
2. Flavanols in dark chocolate have shown an inhibitory effect on angiotensin-converting enzyme activity in vitro
   
   
3. Dark chocolate is rich in flavonoids, which can cause dilation of blood vessels
   
   

Considerations and Limitations

1. A single dose study found that 85% dark chocolate intake actually increased relative values of systolic blood pressure at rest, but buffered cardiovascular reactivity during mental stress
2. While some studies show promising results, the overall effect size of blood pressure reduction in some meta-analyses was considered too small to be clinically significant
3. The quality of some trials is reduced by bias introduced by differences in dosages, lack of appropriate placebos, short follow-up periods, and small sample sizes
   
   

Recommendations

For potential blood pressure benefits, it's suggested to choose dark chocolate with at least 60-70% cocoa content